I don't know if this was part of the same article in the Telegraph but he also wrote the following about the booster seats.
"If people decide that they are not going to comply with this crack-brained law, and they are not going to buy a banquette booster-seat for an 11-year-old, then they will have my complete sympathy. If the overworked police of this country decide they have better things to do than flag motorists down and measure their children to see whether or not they are more than 4ft 5in, then they will have my full support.
If they decide that they are not going to waste their precious time fining parents up to £500 for driving a 134cm 11-year-old without a booster seat then they will, in my view, be exercising robust common sense."
It was introduced following an EU Directive but as far as I'm aware, the legislation (or the legal requirement, if under subsequent legislation) is in effect still.